The adjustment of the North Pacific Subtropical and Subpolar Gyres towards changes in wind stress leads to different time-scale variabilities, which plays a significant role in climate changes. Based on the Sim- ple O...The adjustment of the North Pacific Subtropical and Subpolar Gyres towards changes in wind stress leads to different time-scale variabilities, which plays a significant role in climate changes. Based on the Sim- ple Ocean Data Assimilation （SODA） and Global Ocean Data Assimilation System （GODAS） datasets, the variations of the Subtropical and Subpolar Gyres are diagnosed using ＂three-dimension Ocean Circulation Diagnostic Method＂, and established three types of index series describe the strength, meridional and depth center of the Subtropical and Subpolar Gyres. The above indices present the seasonal, interannual and in- terdecadal variabilities of the Subtropical and Subpolar Gyres, which proves well. Both the Gyres are the strongest in winter, but the Subtropical Gyre is the weakest in summer and the Subpolar Gyre is the weakest in autumn. The Subtropical Gyre moves northward from February to March, southward in October, and to the southernmost in around January, while the Subpolar Gyre moves northward in spring, southward in summer, northward again in autumn and reaching the extreme point in winter to the south. The common feature of the interannual and interdecadal variabilities is that the two gyres were weaker and to the north before 1976-1977, while they were stronger and to the south after 1976-1977. The Subpolar Gyre has made a paramount contribution to the variability on interdecadal scales. As is indicated with the Subpolar Gyre strength indices, there was an important shift from weak to strong around 1976-1977, and the correlation coefficient with the North Pacific Decadal Oscillation （PDO） indices was 0.45, which was far better than that between the Subtropical Gyre strength indices and the PDO. Tests show that influenced by small and mesoscale eddies, the magnitude of large-scale gyres strength is strongly dependent on data resolution. But seasonal interannual and interdecadal large-scale variabilities of the two gyres presented with indices is less affected by model resolution.展开更多
The simulation of a higher-resolution oceanic GCM forced with COADS surface conditions during 1945 ～ 1993 was analyzed with insight into how the North Pacific responds to the surface forcing. The decadal-to-interdeca...The simulation of a higher-resolution oceanic GCM forced with COADS surface conditions during 1945 ～ 1993 was analyzed with insight into how the North Pacific responds to the surface forcing. The decadal-to-interdecadal variabilities in the thermal and dynamical fields especially those associated with the 1976/1977 regime shift in the North Pacific were investigated. The model successfully captures the dominant SST anomaly mode on the decadal-to-interdecadal time scales as well as the major feature of SST anomalies in the 1976/1977 regime shift. The model also successfully reproduces two typical subduction events that link the tropical and extratropical oceanic temperature anomalies during the 1970s and the 1980s. Most importantly, the model simulates the dynamical adjustment of the upper ocean under the surface wind forcing. The typical surface circulation anomaly is characterized by a pattern that is simultaneously related to the wind stress anomalies. The typical anomalous pattern for the entire upper-ocean is characterized by coherent anomalies of two oceanic gyres, i.e. , the subtropical and subpolar gyres. The delayed response and slower adjustment of the gyres, especially of the subpolar gyre, give rise to a persistent SST anomaly in the central North Pacific. The upper-ocean heat budgets in three target regions, i.e. , the central North Pacific, the Californian coastal region and the KOE region, are examined. The cooling in the central North Pacific around 1976/1977 is attributed to the heat flux and mefidional advection anomalies. The associated warming in the Californian coastal region is only due to the heat flux anomaly. A cooling shift in the KOE region which lags that in the central basin by 3 to 4 a is largely due to the meridional advection anomaly and the heat flux acts only as a damping role.展开更多
A dataset of drifting buoys from the Marine Environmental Data Service of Canada was analyzed to map surface circulation of the Pacific. More information of the surface circulation than that acquired before was report...A dataset of drifting buoys from the Marine Environmental Data Service of Canada was analyzed to map surface circulation of the Pacific. More information of the surface circulation than that acquired before was reported in this paper, showing clear and strong western boundary currents, equato- rial currents, and subtropical gyres in the North and South Pacific regions in velocity field, with a more systematic structure in the North Pacific.展开更多
基金The National Natural Science Foundation of China under contract Nos 40976014 and 40805035the Basic Scientific Research and Operation Foundation of the Chinese Academy of Meteorological Sciences,China Meteorological Administration under contract No.2010Z003
文摘The adjustment of the North Pacific Subtropical and Subpolar Gyres towards changes in wind stress leads to different time-scale variabilities, which plays a significant role in climate changes. Based on the Sim- ple Ocean Data Assimilation （SODA） and Global Ocean Data Assimilation System （GODAS） datasets, the variations of the Subtropical and Subpolar Gyres are diagnosed using ＂three-dimension Ocean Circulation Diagnostic Method＂, and established three types of index series describe the strength, meridional and depth center of the Subtropical and Subpolar Gyres. The above indices present the seasonal, interannual and in- terdecadal variabilities of the Subtropical and Subpolar Gyres, which proves well. Both the Gyres are the strongest in winter, but the Subtropical Gyre is the weakest in summer and the Subpolar Gyre is the weakest in autumn. The Subtropical Gyre moves northward from February to March, southward in October, and to the southernmost in around January, while the Subpolar Gyre moves northward in spring, southward in summer, northward again in autumn and reaching the extreme point in winter to the south. The common feature of the interannual and interdecadal variabilities is that the two gyres were weaker and to the north before 1976-1977, while they were stronger and to the south after 1976-1977. The Subpolar Gyre has made a paramount contribution to the variability on interdecadal scales. As is indicated with the Subpolar Gyre strength indices, there was an important shift from weak to strong around 1976-1977, and the correlation coefficient with the North Pacific Decadal Oscillation （PDO） indices was 0.45, which was far better than that between the Subtropical Gyre strength indices and the PDO. Tests show that influenced by small and mesoscale eddies, the magnitude of large-scale gyres strength is strongly dependent on data resolution. But seasonal interannual and interdecadal large-scale variabilities of the two gyres presented with indices is less affected by model resolution.
基金This work wassupported by the National Science Foundation of China （NSFC） under contract Nos 40233028 and 40425009.
文摘The simulation of a higher-resolution oceanic GCM forced with COADS surface conditions during 1945 ～ 1993 was analyzed with insight into how the North Pacific responds to the surface forcing. The decadal-to-interdecadal variabilities in the thermal and dynamical fields especially those associated with the 1976/1977 regime shift in the North Pacific were investigated. The model successfully captures the dominant SST anomaly mode on the decadal-to-interdecadal time scales as well as the major feature of SST anomalies in the 1976/1977 regime shift. The model also successfully reproduces two typical subduction events that link the tropical and extratropical oceanic temperature anomalies during the 1970s and the 1980s. Most importantly, the model simulates the dynamical adjustment of the upper ocean under the surface wind forcing. The typical surface circulation anomaly is characterized by a pattern that is simultaneously related to the wind stress anomalies. The typical anomalous pattern for the entire upper-ocean is characterized by coherent anomalies of two oceanic gyres, i.e. , the subtropical and subpolar gyres. The delayed response and slower adjustment of the gyres, especially of the subpolar gyre, give rise to a persistent SST anomaly in the central North Pacific. The upper-ocean heat budgets in three target regions, i.e. , the central North Pacific, the Californian coastal region and the KOE region, are examined. The cooling in the central North Pacific around 1976/1977 is attributed to the heat flux and mefidional advection anomalies. The associated warming in the Californian coastal region is only due to the heat flux anomaly. A cooling shift in the KOE region which lags that in the central basin by 3 to 4 a is largely due to the meridional advection anomaly and the heat flux acts only as a damping role.
基金Supported by the NSFC (Key Program, No. 90411013)
文摘A dataset of drifting buoys from the Marine Environmental Data Service of Canada was analyzed to map surface circulation of the Pacific. More information of the surface circulation than that acquired before was reported in this paper, showing clear and strong western boundary currents, equato- rial currents, and subtropical gyres in the North and South Pacific regions in velocity field, with a more systematic structure in the North Pacific.
